This subclass contains enzymes that transfer glycosyl groups. Some of these enzymes also catalyse hydrolysis, which can be regarded as transfer of a glycosyl group from the donor to water. Also, inorganic phosphate can act as acceptor in the case of phosphorylases; phosphorolysis of glycogen is regarded as transfer of one sugar residue from glycogen to phosphate. However, the more general case is the transfer of a sugar from an oligosaccharide or a high-energy compound to another carbohydrate molecule that acts as the acceptor. Sub-subclasses are based on the type of sugar residue being transferred: hexosyltransferases (EC 2.4.1), pentosyltransferases (EC 2.4.2) and other glycosyl groups (EC 2.4.99).